1. Field of the Invention
The present invention relates to a method of graphical display of information, in particular survey information.
2. Background of the Art
When a survey is conducted, it is standard practice initially to establish one or more control lines for the survey. As used herein, the term xe2x80x9ccontrol linexe2x80x9d means a straight line of accurately determined length which extends through, or adjacent to, the area to be surveyed; both ends of the control line are very accurately determined xe2x80x98base pointsxe2x80x99 and generally are established by making multiple observations. Alternatively, one or both ends of the control line may be known base points with co-ordinates established from earlier surveys. Depending upon the size of the area to be surveyed, several or many control lines may be established, to build up a network of control lines over the survey area. Typically, all control lines are very accurately surveyed, with multiple observations.
Control lines may be surveyed using any appropriate techniques. For example, if conventional survey techniques using optical survey equipment are used, control lines may be established by means of a traverse survey or a triangulation scheme from a baseline. Alternatively, if global positioning systems (GPS) survey equipment is used, control lines may be established using any of a range of known GPS surveying techniques.
Once each control line has been established, it is usual to complete the survey by making side shots i.e. further survey observations of all significant features in the area being surveyed. The features selected as xe2x80x98significantxe2x80x99 by the surveyor naturally depend upon the purpose of the survey: for example, if the surveying is to produce a topographical map, then the additional significant features will be all major topographical features in the survey area. In a majority of surveys, a very large number of side shots may be made, working from one or more base points on the or each control line. In general, side shots are measured with a lower level of accuracy than the shots to establish the base points and control lines.
Survey data may of course be recorded manually, but modern surveying practice is to record all survey data using a field data collection device and ultimately to input the survey readings into the memory of a computer which is programmed to record and display the surveyed data and to display graphically on the screen the survey points and lines based on that data. As used herein, the term xe2x80x98field data collection devicexe2x80x99 includes a range of suitable devices, including hand-held electronic data collectors and field computers. Field data collection devices usually record the manner in which the data is collected. The present practice is for the computer to display graphically all of the survey lines, so that a complete picture of the survey is created. This works reasonably well for surveys conducted with conventional equipment i.e., optical equipment, since the survey range of optical equipment must be line-of-sight and in most cases it is not feasible to make a very large number of side shots from a single point on a control line using optical equipment. A typical optical survey will have very much shorter control lines than an equivalent GPS survey that is not limited to line of sight. In an optical survey, when side shots are taken over any particular area, the side shots are taken from base points on a series of different control lines, with much fewer side shots from each individual base point. Thus, when these side shots are represented graphically, the side shot lines (i.e. the lines linking each side shot with the corresponding control line base point) are spread along the different control lines.
However, difficulties arise when this display method is used for data obtained from a GPS survey. With GPS surveying equipment, it is not only feasible, but desirable, to make a large number of side shots from a single base point, because the GPS surveying equipment has a substantially greater range than conventional optical equipment. When a large number of side shot observations are displayed graphically as described above, the graphical display shows a dense cluster of lines around the base point from which the observations were made. A typical screen picture of a graphical display of numerous side shot observations is shown in FIG. 1. It is observed that the numerous lines from each side shot to the base point form a dense, unreadable clutter which actually obscures many of the individual shots and also obscures the control line itself.
This drawback makes the graphical display very much less useful than it should be. The surveyor cannot select the control line or an area of side shots for editing since the control line is obscured and conventional editing techniques (typically, boxing an area A on the graphical display) are useless because the area selected contains not only the side shot points but also many of the lines connecting more remote side shots with the base point.
The present invention provides a method and apparatus for displaying survey information in one embodiment. The method includes classifying survey data as important or less/not important, displaying data classified as important as a point and a solid vector from that point, and displaying data classified as not less/not important or less important as a point and a stub vector from that point. The length of each stub vector may be selected such that each stub vector is of sufficient length to provide a visual appreciation of the vector direction but sufficiently short that a majority of the stub vectors in the graphical display do not obscure each other or the rest of the display.